This application claims priority from European Patent Application No. 05016139.7 filed 26 Jul. 2005, the entire disclosure of which is incorporated herein by reference.
The present invention concerns a control stem device such as a winding and time-setting stem for a watch, including a first stem rotating about its longitudinal axis and provided with means for securing it to a manual control crown on the exterior of the watch, and a second rotating stem, substantially parallel and shifted relative to the first and provided with means for selectively driving a winding mechanism and a time-setting mechanism in rotation, the first and second stems being connected in rotation by a transmission device.
The use of two stems shifted in height and kinematically connected, instead of the usual winding stem in a single piece or in two aligned pieces, can be advantageous in a mechanical watch with complications, when the complication elements have to occupy space between the dial and the basic movement and thus lead to the movement being placed lower than the median plane of the watch. The external crown of a conventional winding stem would then be considerably closer to the back cover of the case than to the bezel, which would be both inconvenient and unattractive. The two-stem device allows the crown to be kept in its conventional and convenient place, half way up the case.
In known devices of this type, for example those disclosed in CH Patent No. 691 632 and in EP Patent Application No. 1 1 34 628, the two stems are connected in rotation by a transmission device and are further secured in translation, such that the second stem follows the first when the user pulls out the control crown. Consequently, the second stem, namely the one that extends inside the movement, fulfils all the functions of a conventional stem and has to be fitted with the same members (pull-out piece, sliding pinion, winding pinion, etc.) as a conventional stem. Because of the place occupied by the gear connecting the two stems, the designer is forced to shift these members slightly towards the interior of the movement. Moreover, the connection for securing the two stems in translation requires a mobile frame containing the gear and increasing the space requirement of the device. The axial play that inevitably exists in this frame causes inaccuracies in the axial positions of the first stem, given that the axial position is mainly indexed on the second stem.